Substrate support assembly for high temperature processes

ABSTRACT

An electrostatic chuck includes a ceramic body and adapter objects. The adapter objects collectively form a plurality of openings distributed over a bottom surface of the ceramic body at different distances from a center of a circle defined by the bottom surface of the ceramic body.

RELATED APPLICATION

This application is a continuation application of U.S. patentapplication Ser. No. 15/061,734, filed on Mar. 4, 2016, which isincorporated by reference herein.

TECHNICAL FIELD

Some embodiments of the present invention relate, in general, to asubstrate support assembly that is usable for high temperatureprocesses.

BACKGROUND

Electrostatic chucks are widely used to hold substrates, such assemiconductor wafers, during substrate processing in processing chambersused for various applications, such as physical vapor deposition,etching, or chemical vapor deposition. Electrostatic chucks typicallyinclude one or more electrodes embedded within a unitary chuck bodywhich includes a dielectric or semi-conductive ceramic material acrosswhich an electrostatic clamping field can be generated.

Electrostatic chucks offer several advantages over mechanical clampingdevices and vacuum chucks. For example, electrostatic chucks reducestress-induced cracks caused by mechanical clamping, allow larger areasof the substrate to be exposed for processing (little or no edgeexclusion), and can he used in low pressure or high vacuum environments.Additionally, the electrostatic chuck can hold the substrate moreuniformly to a chucking surface to allow a greater degree of controlover substrate temperature.

Various processes used in the fabrication of integrated circuits maycall for high temperatures and/or wide temperature ranges for substrateprocessing. For example, electrostatic chucks in etch processestypically operate in a temperature range of up to about 120° C. Attemperatures above about 120° C., the components of many electrostaticchucks will begin to fail due to various issues such as de-chucking inAl₂O₃ electrostatic chucks, plasma erosion from corrosive chemistry,bond reliability, and so on.

SUMMARY

Some embodiments of the present invention described herein cover anelectrostatic chuck comprising a ceramic body having a top and a bottom,one or more heating elements disposed in the ceramic body, and one ormore electrodes disposed in the ceramic body. The electrostatic chuckfurther comprises a plurality of objects bonded to the bottom of theceramic body by a metal bond, wherein collectively the plurality ofobjects comprise a plurality of features distributed over the bottom ofthe ceramic body at a plurality of different distances from a center ofa circle defined by the bottom of the ceramic body, and wherein afeature of the plurality of features accommodates a fastener.

Some embodiments of the present invention described herein cover asubstrate support assembly that includes an electrostatic chuckcomprising one or more objects bonded to a bottom of the electrostaticchuck by a metal bond, wherein collectively the one or more objectscomprise a plurality of features distributed over the bottom of theelectrostatic chuck at a plurality of different distances from a centerof a circle defined by the bottom of the electrostatic chuck, andwherein collectively the plurality of features accommodate a pluralityof fasteners. The substrate support assembly further includes a baseplate coupled to the electrostatic chuck by the plurality of fasteners,wherein the plurality of fasteners each apply an approximately equalfastening force to couple the base plate to the electrostatic chuck. Thesubstrate support assembly further includes an o-ring disposed betweenthe electrostatic chuck and the base plate at a periphery of theelectrostatic chuck.

Some embodiments of the present invention described herein cover a baseplate for a substrate support assembly that includes a metal bodycomprising a recess, the metal body comprising one or more features thataccommodate a fastener. The base plate further includes a metal coolingplate disposed in the recess, the metal cooling plate comprising aplurality of channels to receive a coolant, the metal cooling platefurther comprising one or more surface features on a top of the metalcooling plate. The base plate further includes a plurality of springsthat connect a bottom of the metal cooling plate to the metal body and athermal gasket on the top of the cooling plate, the thermal gasketcomprising one or more layers of polyimide and a plurality of layers ofgrafoil.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are illustrated by way of example,and not by way of limitation, in the figures of the accompanyingdrawings in which like references indicate similar elements. It shouldbe noted that different references to “an” or “one” embodiment in thisdisclosure are not necessarily to the same embodiment, and suchreferences mean at least one.

FIG. 1 depicts a sectional side view of one embodiment of a processingchamber.

FIG. 2 depicts an exploded view of one embodiment of a substrate supportassembly.

FIG. 3 depicts a sectional top view of one embodiment of a substratesupport assembly.

FIG. 4A depicts a perspective view of one embodiment of an electrostaticchuck.

FIG. 4B depicts a perspective view of another embodiment of anelectrostatic chuck.

FIG. 5 depicts a sectional side view of one embodiment of a substratesupport assembly.

FIG. 6A depicts a perspective view of one embodiment of an electrostaticchuck.

FIG. 6B depicts a perspective view of another embodiment of anelectrostatic chuck.

FIG. 7 depicts a sectional side view of one embodiment of a substratesupport assembly.

FIG. 8 illustrates one embodiment of a process for manufacturing asubstrate support assembly.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention provide an electrostatic chuck thatincludes multiple adapter objects bonded to a bottom of theelectrostatic chuck by a metal bond. The adapter objects in oneembodiment are discs and/or rings that each include multiple featuresfor receiving a fastener. In another embodiment, the adapter objects arediscs or objects having other shape that each include one or a fewfeatures for receiving a fastener. The adapter objects may be bonded toa flat bottom of the electrostatic chuck or may be inserted into andbonded to recesses formed on the bottom of the electrostatic chuck.

Embodiments further provide a substrate support assembly that includesthe electrostatic chuck having the multiple adapter objects bonded tothe bottom of the electrostatic chuck. The substrate support assemblymay additionally include a base plate having a spring loaded coolingplate that presses against the electrostatic chuck. The cooling platemay include a gasket with low thermal conductivity that acts as athermal choke between the cooling plate and the electrostatic chuck. Useof the spring loaded cooling plate including the gasket may enable theelectrostatic chuck to maintain a temperature that is up to 200 or 300degrees Celsius hotter than a temperature of the cooling plate.

The electrostatic chuck may be coupled to the base plate by a collectionof fasteners, where each of the fasteners is inserted into one of theadapter objects bonded to the bottom of the electrostatic chuck. Themultiple fasteners are located at different distances from a center of acircle defined by the bottom of the electrostatic chuck. In oneembodiment, a first set of fasteners are disposed at a first radius fromthe center of the electrostatic chuck and a second set of fasteners aredisposed at a second radius from the center of the electrostatic chuck.The multiple fasteners may be approximately uniformly distributed acrossthe bottom of the electrostatic chuck to evenly distribute a fasteningforce to couple the electrostatic chuck to the base plate. The fastenersmay all be tightened an equal amount to ensure that the fastening forcesapplied by each fastener is about the same. This facilitates uniformheat transfer properties between the electrostatic chuck and the coolingplate over the electrostatic chuck.

In some embodiments, a high temperature o-ring or gasket is compressedbetween the base plate and the electrostatic chuck. The high-temperatureo-ring or gasket may protect the adapter objects from exposure toprocessing gasses. Additionally, the electrostatic chuck may include agas delivery hole that aligns with a gas delivery hole in the baseplate. An o-ring may be disposed around the gas delivery holes andcompressed between the electrostatic chuck and the base plate.

FIG. 1 is a sectional view of one embodiment of a semiconductorprocessing chamber 100 having a substrate support assembly 150 disposedtherein. The substrate support assembly 150 includes an electrostaticchuck 166 that includes multiple adapter objects 167 bonded to a bottomof the electrostatic chuck 166, as will be discussed in greater detailbelow. The electrostatic chuck 166 is coupled to a cooling plate bymultiple fasteners, as discussed in greater detail below.

The processing chamber 100 includes a chamber body 102 and a lid 104that enclose an interior volume 106. The chamber body 102 may befabricated from aluminum, stainless steel or other suitable material.The chamber body 102 generally includes sidewalls 108 and a bottom 110.An outer liner 116 may be disposed adjacent the side walls 108 toprotect the chamber body 102. The outer liner 116 may be fabricatedand/or coated with a plasma or halogen-containing gas resistantmaterial. In one embodiment, the outer liner 116 is fabricated fromaluminum oxide. In another embodiment, the outer liner 116 is fabricatedfrom or coated with yttria, yttrium alloy or an oxide thereof.

An exhaust port 126 may be defined in the chamber body 102, and maycouple the interior volume 106 to a pump system 128. The pump system 128may include one or more pumps and throttle valves utilized to evacuateand regulate the pressure of the interior volume 106 of the processingchamber 100.

The lid 104 may be supported on the sidewall 108 of the chamber body102. The lid 104 may be opened to allow access to the interior volume106 of the processing chamber 100, and may provide a seal for theprocessing chamber 100 while closed. A gas panel 158 may be coupled tothe processing chamber 100 to provide process and/or cleaning gases tothe interior volume 106 through a gas distribution assembly 130 that ispart of the lid 104. Examples of processing gases may be used to processin the processing chamber including halogen-containing gas, such asC₂F₆, SF₆, SiCl₄, HBr, NF₃, CF₄, CHF₃, CH₂F₃, Cl₂ and SiF₄, amongothers, and other gases such as O₂, or N₂O. Examples of carrier gasesinclude N₂, He, Ar, and other gases inert to process gases (e.g.,non-reactive gases). The gas distribution assembly 130 may have multipleapertures 132 on the downstream surface of the gas distribution assembly130 to direct the gas flow to the surface of the substrate 144.Additionally, or alternatively, the gas distribution assembly 130 canhave a center hole where gases are fed through a ceramic gas nozzle. Thegas distribution assembly 130 may be fabricated and/or coated by aceramic material, such as silicon carbide, Yttrium oxide, etc. toprovide resistance to halogen-containing chemistries to prevent the gasdistribution assembly 130 from corrosion.

The substrate support assembly 150 is disposed in the interior volume106 of the processing chamber 100 below the gas distribution assembly130. The substrate support assembly 150 holds a substrate 144 duringprocessing. An inner liner 118 may be coated on the periphery of thesubstrate support assembly 150. The inner liner 118 may be ahalogen-containing gas resist material such as those discussed withreference to the outer liner 116. In one embodiment, the inner liner 118may be fabricated from the same materials of the outer liner 116.

In one embodiment, the substrate support assembly 150 includes amounting plate 162 supporting a pedestal 152, a base plate 164 andelectrostatic chuck 166. In one embodiment, the base plate 164 iscoupled to the electrostatic chuck 166 by multiple fasteners. In oneembodiment, the base plate 164 includes a thermally conductive basereferred to herein as a cooling plate. The substrate support assembly150 described in embodiments may be used for Johnsen-Rahbek and/orCoulombic electrostatic chucking.

In one embodiment, a protective ring 146 is disposed over a portion ofthe electrostatic chuck 166 at an outer perimeter of the electrostaticchuck 166. In one embodiment, the electrostatic chuck 166 is coated witha protective layer 136. Alternatively, the electrostatic chuck 166 maynot be coated by a protective layer 136. The protective layer 136 may bea ceramic such as Y₂O₃ (yttria or yttrium oxide), Y₄Al₂O₉ (YAM), Al₂O₃(alumina), Y₃Al₅O₁₂ (YAG), YAlO3 (YAP), Quartz, SiC (silicon carbide),Si₃N₄ (silicon nitride) Sialon, AlN (aluminum nitride), AlON (aluminumoxynitride), TiO₂ (titania), ZrO₂ (zirconia), TiC (titanium carbide),ZrC (zirconium carbide), TiN (titanium nitride), TiCN (titanium carbonnitride), Y₂O₃ stabilized ZrO₂ (YSZ), and so on. The protective layermay also be a ceramic composite such as Y₃Al₅O₁₂ distributed in Al₂O₃matrix, Y₂O₃—ZrO₂ solid solution or a SiC—Si₃N₄ solid solution. Theprotective layer may also be a ceramic composite that includes a yttriumoxide (also known as yttria and Y₂O₃) containing solid solution. Forexample, the protective layer may be a ceramic composite that iscomposed of a compound Y₄Al₂O₉ (YAM) and a solid solution Y₂—xZr_(x)O₃(Y₂O₃—ZrO₂ solid solution). Note that pure yttrium oxide as well asyttrium oxide containing solid solutions may be doped with one or moreof ZrO₂, Al₂O₃, SiO₂, B₂O₃, Er₂O₃, Nd₂O₃, Nb₂O₅, CeO₂, Sm₂O₃, Yb₂O₃, orother oxides. Also note that pure Aluminum Nitride as well as dopedAluminum Nitride with one or more of ZrO₂, Al₂O₃, SiO₂, B₂O₃, Er₂O₃,Nd₂O₃, Nb₂O₅, CeO₂, Sm₂O₃, Yb₂O₃, or other oxides may be used.Alternatively, the protective layer may be sapphire or MgAlON.

The electrostatic chuck 166 may be or include a puck made of adielectric or electrically insulative material (e.g., having anelectrical resistivity of greater than 10¹⁴ Ohm·meter) that is usablefor semiconductor processes at temperatures of 180° C. and above. In oneembodiment, the electrostatic chuck 166 is composed of materials usablefrom about 20° C. to about 500° C. In one embodiment, the electrostaticchuck 166 is AlN. The AlN electrostatic chuck 166 may be undoped or maybe doped. For example, the AlN may be doped with Samarium oxide (Sm₂O₃),Cerium oxide (CeO₂), Titanium dioxide (TiO₂), or a transition metaloxide. In one embodiment, the electrostatic chuck 166 is Al₂O₃. TheAl₂O₃ electrostatic chuck 166 may be undoped or may be doped. Forexample, the Al₂O₃ may be doped with Titanium dioxide (TiO₂) or atransition metal oxide.

One or more adapter objects 167 may be bonded to a bottom of theelectrostatic chuck 166. The adapter objects 167 may have a coefficientof thermal expansion that is approximately matched to a coefficient ofthermal expansion of the electrostatic chuck 166. In one embodiment, theadapter objects 167 are made of a SiC porous body that is infiltratedwith an AlSi alloy (referred to as AlSiSiC). In one embodiment, theadapter objects 167 are molybdenum. Other materials may also be used.

The mounting plate 162 may be coupled to the bottom 110 of the chamberbody 102 and includes passages for routing utilities (e.g., fluids,power lines, sensor leads, etc.) to the base plate 164 and theelectrostatic chuck 166. The base plate 164 and/or electrostatic chuck166 may include one or more optional embedded heating elements 176,optional embedded thermal isolators 174 and/or optional conduits 168,170 to control a lateral temperature profile of the substrate supportassembly 150. In one embodiment, a thermal gasket 138 is disposed on atleast a portion of the base plate 164.

The conduits 168, 170 may be fluidly coupled to a fluid source 172 thatcirculates a temperature regulating fluid through the conduits 168, 170.The embedded thermal isolators 174 may be disposed between the conduits168, 170 in one embodiment. The embedded heating elements 176 areregulated by a heater power source 178. The conduits 168, 170 andembedded heating elements 176 may be utilized to control the temperatureof the electrostatic chuck 166, and for heating and/or cooling theelectrostatic chuck 166 and a substrate (e.g., a wafer) being processed.In one embodiment, the electrostatic chuck 166 includes two separateheating zones that can maintain distinct temperatures. In anotherembodiment, the electrostatic chuck 166 includes four different heatingzones that can maintain distinct temperatures. More or fewer heatingzones may also be used. The temperature of the electrostatic chuck 166and the base plate 164 may be monitored using multiple temperaturesensors 190, 192 that may be monitored using a controller 195.

The electrostatic chuck 166 may further include multiple gas passagessuch as grooves, mesas and other surface features that may be formed inan upper surface of the electrostatic chuck 166. The gas passages may befluidly coupled to a source of a heat transfer (or backside) gas, suchas He via holes drilled in the puck 166. In operation, the backside gasmay be provided at controlled pressure into the gas passages to enhancethe heat transfer between the electrostatic chuck 166 and the substrate144.

In one embodiment, the electrostatic chuck 166 includes at least oneclamping electrode 180 controlled by a chucking power source 182. Theclamping electrode 180 (also referred to as a chucking electrode) mayfurther be coupled to one or more RF power sources 184, 186 through amatching circuit 188 for maintaining a plasma formed from process and/orother gases within the processing chamber 100. The one or more RF powersources 184, 186 are generally capable of producing an RF signal havinga frequency from about 50 kHz to about 3 GHz and a power of up to about10,000 Watts. In one embodiment, an RF signal is applied to the metalbase, an alternating current (AC) is applied to the heater and a directcurrent (DC) is applied to the clamping electrode 180.

FIG. 2 depicts an exploded view of one embodiment of the substratesupport assembly 150 including the electrostatic chuck 166, the mountingplate 162, the base plate 164, a cooling plate 165, and the pedestal152. As shown, in one embodiment a base plate 164 may include an innerrecess, and the cooling plate 165 may be inserted into and attached tothe inner recess. An o-ring (not shown) may be disposed over the baseplate 164 at a periphery 240 of the base plate 164. In one embodiment,the o-ring is a perfluoropolymer (PFP) o-ring. Alternatively, othertypes of high temperature o-rings may be used. In one embodiment,thermally insulating high temperature o-rings are used. The o-ring maybe a stepped o-ring having a first step at a first thickness and asecond step at a second thickness. This may facilitate uniformtightening of fasteners by causing the amount of force used to tightenthe fasteners to increase dramatically after a set amount of compressionof the PFP o-ring.

Additional o-rings (not shown) may also be disposed on the top side ofthe cooling plate 165 and/or base plate 164 around a hole 280 at acenter of the cooling plate 165 through which cables are run. Othersmaller o-rings may also be disposed on the cooling plate 165 and/orbase plate 164 around other openings, around lift pins, and so forth.The o-rings provide a vacuum seal between a chamber interior volume andinterior volumes within the substrate support assembly 150. The interiorvolumes within the substrate support assembly 150 include open spaceswithin the pedestal 152 for routing conduits and wiring.

In one embodiment, a gasket (e.g., a PFP gasket) may be disposed on thetop side of the cooling plate 165. Examples of PFPs usable for thegasket or o-ring are Dupont's™ ECCtreme™, Dupont's KALREZ® and Daikin's®DUPRA™. Alternatively, the gasket may be a stack of alternating layersof grafoil and polyimide.

The cooling plate 165 and/or base plate 164 additionally includenumerous features 242 through which fasteners are inserted. The gasketmay have cutouts at each of the features 242 in some embodiments.

Fasteners extend through each of the features 242 and attach toadditional portions of the fasteners (or to additional fasteners) thatare inserted into additional features formed in adapter objects bondedto the electrostatic chuck 166. For example, a bolt may extend through afeature 242 in the cooling plate 165 and be screwed into a nut disposedin a feature of the electrostatic chuck 166. Alternatively, fastenersmay extend through features 242 and attach to features formed in theadapter objects bonded to the bottom of the electrostatic chuck 166.Each feature 242 in the cooling plate 165 may line up to a similarfeature (not shown) in electrostatic chuck 166.

The electrostatic chuck 166 has a disc-like shape having an annularperiphery 230 that may substantially match the shape and size of thesubstrate 144 positioned thereon. An upper surface of the electrostaticchuck 166 may have an outer ring 216, multiple mesas 206, 210 andchannels 208, 212 between the mesas 210. The electrostatic chuck 166includes a lip 232 that rests on the outer periphery 240 of the baseplate 164. In one embodiment, the electrostatic chuck 166 may befabricated by an electrically insulative ceramic material. Suitableexamples of the ceramic materials include aluminum nitride (AlN),alumina (Al₂O₃), and the like.

The electrostatic chuck 166 may include two or more adapter objects (notshown) bonded to a bottom of the electrostatic chuck 166. Each adapterobject may include one or more features (not shown) for receivingfasteners. The features may be approximately evenly distributed across asurface of the electrostatic chuck 166, and may include a first set offeatures at a first distance from a center of a circle defined by thebottom of the electrostatic chuck 166 and a second set of features at asecond distance from the center of the circle defined by the bottom ofthe electrostatic chuck 166.

The base plate 164 attached below the electrostatic chuck 166 may have adisc shape and be positioned on the mounting plate 162. In oneembodiment, the base plate 164 may be fabricated by a metal, such asaluminum or stainless steel or other suitable materials. In oneembodiment, the cooling plate 165 may be fabricated from a metal such asaluminum, stainless steel, or other materials. Alternatively, thecooling plate 165 may be fabricated by a composite ceramic, such as analuminum-silicon alloy infiltrated SiC or Molybdenum to match a thermalexpansion coefficient of the electrostatic chuck 166.

FIG. 3 depicts a sectional top view of one embodiment of anelectrostatic chuck 166. As shown, the electrostatic chuck 166 has aradius R3, which may be substantially similar to a radius of substratesor wafers that are to be supported by the electrostatic chuck 166. Theelectrostatic chuck 166 additionally includes multiple features 305. Thefeatures may match similar features in a cooling plate to which theelectrostatic chuck 166 is mounted. Each feature 305 accommodates afastener. For example, a bolt (e.g., a stainless steel bolt, galvanizedsteel bolt, etc.) may be placed into each feature such that a head ofthe bolt is inside of an opening large enough to accommodate the headand a shaft of the bolt extends out of a bottom side of theelectrostatic chuck 166. The bolt may be tightened onto a nut that isplaced in a corresponding feature in the cooling plate. Alternatively,features 305 may be sized to accommodate a nut, and may include a holethat can receive a shaft of a bolt that is accommodated by acorresponding feature in the cooling plate. In another example, ahelical insert (e.g., a Heli-Coil®) or other threaded insert (e.g., apress fit insert, a mold-in insert, a captive nut, etc.) may be insertedinto one or more of the features to add a threaded hole thereto. In oneembodiment, the features 305 are threaded holes into which a bolt orthreaded rod may be inserted. A bolt placed inside of the base plate andprotruding from the cooling plate may then be threaded into the threadedinsert or threaded feature to secure the base plate and cooling plate tothe electrostatic chuck 166. Alternatively, or additionally, threadedinserts may be used in the cooling plate and/or base plate.

The features 305 may be slightly oversized as compared to a size of thefasteners in some embodiments to accommodate a greater coefficient ofthermal expansion of the fasteners. In one embodiment, the fasteners aresized such that the fasteners will not exert a force on the featureswhen the fasteners are heated to 500 or 600 degrees Celsius.

As shown, multiple sets of features 305 may be included in theelectrostatic chuck 166. Each set of features 305 may be evenly spacedat a particular radius or distance from a center of a circle defines bythe electrostatic chuck 166. For example, as shown a first set offeatures 305 is located at a radius R1 and a second set of features 305is located at a radius R2. Additional sets of features may also belocated at additional radii.

In one embodiment, the features 305 are arranged to create a uniformload on the electrostatic chuck 166. In one embodiment, the features arearranged such that a bolt is located approximately every 30-70 squarecentimeters (e.g., every 50 square centimeters). In one embodiment,three sets of features are used for a 12 inch electrostatic chuck 166. Afirst set of features may be located about 4 inches from a center of theelectrostatic chuck 166 and includes about 4 features. A second set offeatures may be located about 6 inches from a center of theelectrostatic chuck 166 and includes about 6 features. A third set offeatures may be located about 8 inches from a center of theelectrostatic chuck 166 and includes about 8 features. In oneembodiment, the electrostatic chuck 166 includes about 8-24 featuresarranged in sets at 2-3 different radii, where each feature accommodatesa fastener.

FIG. 4A depicts a perspective view of one embodiment of a bottom of anelectrostatic chuck 400. The electrostatic chuck 400 is shown upsidedown to better show particular components of the electrostatic chuck400. As illustrated, the bottom of the electrostatic chuck 400 defines acircle. Multiple holes have been drilled into the bottom of theelectrostatic chuck, and adapter objects 420, 424 have been insertedinto those holes and bonded to the electrostatic chuck 400 using a metalbond. Each of the adapter objects 420, 424 includes one or more features422, 426. For example, adapter objects 420 near a periphery of theelectrostatic chuck 400 include features 422 and adapter objects 424near a center of the circle defined by the bottom of the electrostaticchuck 400 include features 426. As illustrated, each adapter object 420,424 has a circular shape and includes a single feature 422, 426.However, in alternative embodiments adapter objects 420, 424 may havedifferent shapes, have different sizes and/or contain more than onefeature. For example, adapter objects 420, 424 may be square,rectangular, hexagonal, octagonal, or have other shapes.

Electrostatic chuck 400 may additionally include one or more lift pinholes 499 and/or a gas delivery hole 480. In the illustrated example, aline A1-A1′ is shown that passes through two outer adapter objects 420,two inner adapter objects 424 and the gas delivery hole 480.

FIG. 4B depicts a perspective view of one embodiment of a bottom of anelectrostatic chuck 402. The electrostatic chuck 402 is shown upsidedown to better show particular components of the electrostatic chuck402. As illustrated, the bottom of the electrostatic chuck 402 defines acircle. Two ring shaped trenches have been machined into the bottom ofthe electrostatic chuck 402, and adapter objects 430, 440 have beeninserted into those ring shaped trenches and bonded to the electrostaticchuck 402 using a metal bond. Each of the adapter objects 430, 440includes multiple features 432, 442. For example, adapter object 430near a periphery of the electrostatic chuck 402 include features 432 andadapter object 440 near a center of the circle defined by the bottom ofthe electrostatic chuck 402 include features 442. As illustrated,adapter object 430 and 440 each have a ring shape and includes multiplefeatures 432, 442. However, in alternative embodiments adapter objects430, 440 may have different shapes, have different sizes and/or containdifferent amounts of features. For example, an electrostatic chuck mayinclude one or more straight rectangular adapter objects, some of whichmay include features near the center of the electrostatic chuck as wellas features near the periphery of the electrostatic chuck. Anelectrostatic chuck may additionally or alternatively include adapterobjects having a shape of a partial ring that include multiple outerfeatures or multiple inner features.

Electrostatic chuck 402 may additionally include one or more lift pinholes 499 and/or a gas delivery hole 480. In the illustrated example, aline A2-A2′ is shown that passes through adapter object 430, adapterobject 440 and the gas delivery hole 480.

FIG. 5 depicts a sectional side view of one embodiment of a substratesupport assembly 505. In one embodiment, substrate support assembly 505corresponds to substrate support assembly 150 of FIGS. 1-2. Thesubstrate support assembly 505 includes an electrostatic chuck 515, abase plate 595, a cooling plate 536 and a mounting plate 540.

In one embodiment, electrostatic chuck 515 corresponds to electrostaticchuck 400 of FIG. 4A. The sectional side view of FIG. 5 is shown at acut line that corresponds to line A1-A1′ of FIG. 4A in one embodiment.In one embodiment electrostatic chuck 515 corresponds to electrostaticchuck 402. of FIG. 4B. The sectional side view of FIG. 5 is shown at acut line that corresponds to line A2-A2′ of FIG. 4B in one embodiment.

The electrostatic chuck 515 is composed of an electrically insulative(dielectric) ceramic such as AlN or Al₂O₃. The electrostatic chuck 515includes clamping electrodes 527 and one or more heating elements 529.The clamping electrodes 527 may be coupled to a chucking power source(not shown), to an RF plasma power supply (not shown) and/or to an RFbias power supply (not shown) via a matching circuit (not shown). Theheating elements 529 are electrically connected to a heater power source(not shown) for heating the electrostatic chuck 515.

In one embodiment, the electrostatic chuck 515 includes multiplerecesses 563, 567. The recesses 563, 567 may be holes and/or trenches ofvarying shape, depth and size. In the embodiments where electrostaticchuck 515 corresponds to electrostatic chuck 400 of FIG. 4A, therecesses 563 and 567 are circular holes, and there are multiple distinctrecesses 563 and multiple distinct recesses 567. In the embodimentswhere electrostatic chuck 515 corresponds to electrostatic chuck 402 ofFIG. 4B, the recesses 563 are a ring shaped trench and the recesses 567are another ring shaped trench.

Recess 563 includes an adapter object 552 that is bonded to the recess563 by a metal bond 550. The adapter object 552 may be bonded to thebottom of the electrostatic chuck in the recess 563. Similarly, recess567 includes an adapter object 562 that is bonded to the recess 567 by ametal bond 550. The adapter object 562 may be bonded to the bottom ofthe electrostatic chuck in the recess 567. Adapter object 552 includesone or more features 554. Adapter object 562 additionally includes oneor more features 564. Each feature is configured to receive a fastener,as is described in greater detail below.

Preferably, the adapter objects 552, 562 are made of a material having aCTE that matches or is similar to a CTE of the electrostatic chuck 515.In one embodiment, the adapter objects 552, 562 are molybdenum. Inanother embodiment, the adapter objects are made of a nickel-cobaltferrous alloy such as Kovar®.

In another embodiment, the adapter objects 552, 562 are made of anelectrically conductive metal matrix composite (MMC) material. The MMCmaterial includes a metal matrix and a reinforcing material which isembedded and dispersed throughout the matrix. The metal matrix mayinclude a single metal or two or more metals or metal alloys. Metalswhich may be used include but are not limited to aluminum (Al),magnesium (Mg), titanium (Ti), cobalt (Co), cobalt-nickel alloy (CoNi),nickel (Ni), chromium (Cr), or various combinations thereof. Thereinforcing material may be selected to provide the desired structuralstrength for the MMC, and may also be selected to provide desired valuesfor other properties of the MMC, such as thermal conductivity and CTE,for example. Examples of reinforcing materials which may be used includesilicon (Si), carbon (C), or silicon carbide (SiC), but other materialsmay also be used.

The MMC material is preferably chosen to substantially match the CTE ofthe electrostatic chuck 515 over the operating temperature range for thesubstrate support assembly 505. In one embodiment, the temperature mayrange from about 20° Celsius to about 500° Celsius. In one embodiment,matching the CTEs is based on selecting the MCC material so that the MCCmaterial includes at least one material which is also used in theelectrostatic chuck 515. In one embodiment, the electrostatic chuck 515includes AlN. In one embodiment, the MMC material includes a SiC porousbody that is infiltrated with an AlSi alloy (referred to herein asAlSiSiC).

The constituent materials and composition percentages of the MMC may beselected to provide an engineered material which meets desirable designobjectives. For example, by suitably selecting the MCC material toclosely match the CTE of the electrostatic chuck 515, thethermo-mechanical stresses at an interface between the adapter objects552, 562 and the electrostatic chuck 515 are reduced.

By matching coefficients of thermal expansion between the adapterobjects 552, 562 and the electrostatic chuck 515, stress caused bybonding the adapter objects 552, 562 to the electrostatic chuck 515 maybe minimized. In one embodiment, diffusion bonding is used as the methodof metal bonding to produce the metal bond 550. In another embodiment,brazing is used to produce the metal bond 550. However, other bondingmethods may also be used to produce the metal bond.

Metal bond 550 may include an “interlayer” of aluminum foil or othermetal foil that is placed in a bonding region between the electrostaticchuck 515 and the adapter object 552, 562. Pressure and heat may beapplied to form a diffusion bond between the aluminum foil and theelectrostatic chuck 515 and between the aluminum foil and adapter object552, 562. In other embodiments, the diffusion bonds may be formed usingother interlayer materials which are selected based upon the materialsused for electrostatic chuck 515 and the adapter object 552, 562. In oneembodiment, the metal bond 550 has a thickness of about 0.2-0.3 mm. Inone embodiment, the electrostatic chuck 515 may be directly bonded tothe adapter object 552, 562 using direct diffusion bonding in which nointerlayer is used to form the bond.

The electrostatic chuck 515 may have a thickness of about 5-35 mm. Inone embodiment, the electrostatic chuck 515 has a thickness of about8-15 mm. The clamping electrodes 527 may be located about 0.3 to 1 mmfrom an upper surface of the electrostatic chuck 515, and the heatingelements 529 may be located about 2 mm under the clamping electrodes527. The heating elements 529 may be screen printed heating elementshaving a thickness of about 10-200 microns. Alternatively, the heatingelements 529 may be resistive coils that use about 1-3 mm of thicknessof the electrostatic chuck 515. In one embodiment, the electrostaticchuck 515 additionally includes enough additional thickness toaccommodate the recesses 563, 567 and inserted adapter objects 552, 562.The adapter objects 552, 562 may have a thickness of about 5 mm to about25 mm in some embodiments.

In one embodiment, the electrostatic chuck 515 has a diameter of about300 mm. Alternatively, the electrostatic chuck 515 may have any otherdiameter. An edge of base plate 595 may have a similar diameter to thediameter of the electrostatic chuck 515. A plasma resistant and hightemperature o-ring 545 may be disposed between electrostatic chuck 515and the base plate 595. This o-ring 545 may provide a vacuum sealbetween an interior of the substrate support assembly 505 and aprocessing chamber. The o-ring 545 may be made of a perfluoropolymer(PFP). In one embodiment, the o-ring 545 is a PFP with inorganicadditives such as SiC. The o-ring 545 may be replaceable.

The base plate 595 includes a cooling plate 536 that may act as a heatsink for the electrostatic chuck 515. The material of the cooling plate536 may affect the heat transfer properties of the cooling plate 536.For example, an aluminum cooling plate 536 will transfer heat betterthan a stainless steel cooling plate 536.

The cooling plate 536 may be coupled to the base plate 595 by one ormore springs 570, which operate to press the heat sink 536 against theelectrostatic chuck 515. In one embodiment, the springs 570 are coilsprings. The springs 570 apply a force to press the heat sink 536against the electrostatic chuck 515. The electrostatic chuck 515 iscoupled to and in thermal communication with the cooling plate 536. Thecooling plate 536 has one or more conduits 535 (also referred to hereinas cooling channels) in fluid communication with a fluid source (notshown).

The adapter objects 552, 562 may collectively include numerous features554, 564 for receiving fasteners. The base plate 595 may likewiseinclude multiple features 526 for accommodating the fasteners.Additionally, the cooling plate 536 may include multiple bores foraccommodating the fasteners. In one embodiment, the cooling plate 536and/or base plate 595 are coupled to the electrostatic chuck 515 bymultiple fasteners 528. The fasteners 528 may be threaded fasteners suchas bolts or nut and bolt pairs.

In one embodiment, the features 526 are bolt holes with counter bores.The features may be through features that extend through the base plate595. In one embodiment, the features 554, 564 are threaded holes in theadapter objects 552, 562. Alternatively, the features may be holesand/or slots that accommodate a t-shaped bolt head or rectangular nutthat may be inserted into the slot and then rotated 90 degrees. In oneembodiment, a helical insert (e.g., a Heli-Coil®) or other threadedinsert (e.g., a press fit insert, a mold-in insert, a captive nut, etc.)may be inserted into features 554 to add a threaded hole thereto. A boltplaced inside of the cooling plate 536 and/or base palate 595 (e.g.,inside features 526 in the base plate 595 through the cooling plate 536)and protruding from the cooling plate 536 may then be threaded into thethreaded insert or the threaded hole to secure the cooling plate to thepuck. In one embodiment, the fasteners include washers, grafoil,aluminum foil, or other load spreading materials to distribute forcesfrom a head of the fastener evenly over a feature.

In one embodiment, the features 554, 564 are threaded holes that arebrazed prior to insertion of a threaded rod into the features 554, 564.A metal bonding (e.g., diffusion bonding) procedure may then beperformed to secure the threaded rod to the feature 554, 564. This mayprovide increased durability for application of increased force duringassembly.

The cooling plate 536 may act as a heat sink to absorb heat from theelectrostatic chuck 515. In one embodiment (as shown), a low thermalconductivity gasket 525 is disposed on the cooling plate 436. The lowthermal conductivity gasket 525 may be, for example, a PFP gasket thatis disposed on the cooling plate 536. The PFP gasket may have a thermalconductivity of about 0.2 Watts per meter Kelvin (W/(mK)) or lower.

Alternatively, the low thermal conductivity gasket 525 may be analternating stack of grafoil and polyimide layers. For example, the lowthermal conductivity gasket 525 may be a stack of a first grafoil layer,a polyimide layer on the first grafoil layer, and a second grafoil layeron the polyimide layer. In another example, the low thermal conductivitygasket 525 may be a stack of a first grafoil layer, a first polyimidelayer on the first grafoil layer, a second grafoil layer on the firstpolyimide layer, a second polyimide layer on the second grafoil layer,and a third grafoil layer on the second polyimide layer.

The polyimide layers may have a very low thermal conductivity of about0.2 Watts per meter Kelvin (W/(m·K)). However, the polyimide may have alow compressibility. The low compressibility may reduce a contact areabetween the electrostatic chuck 515 and the cooling plate 536 if thepolyimide is used by itself to form the low thermal conductivity gasket525. The grafoil layers have a high thermal conductivity, but also havea high compressibility. Graphoil may have an in plane thermalconductivity of 240 W/(m·K) and a through plane thermal conductivity of5 W/(m·K). Accordingly, by using an alternating stack of grafoil andpolyimide the low thermal conductivity gasket 525 may have both a mediumto high compressibility and a low thermal conductivity. Thecompressibility of polyimide is about 1-2% and the compressibility ofgrafoil is about 5-10% in embodiments.

The fasteners 528 may be tightened with approximately the same force toevenly compress the high temperature o-ring 545 and/or other o-rings.The low thermal conductivity gasket 525 may decrease heat transferbetween the electrostatic chuck 515 and the cooling plate 536 and act asa thermal choke. In one embodiment, a grafoil layer (not shown) isdisposed over the low thermal conductivity gasket 525. The grafoil mayhave a thickness of about 10-40 mil. The fasteners may be tightened tocompress the grafoil layer as well as the low thermal conductivitygasket 525.

By maintaining a thermal choke between the electrostatic chuck 515 andthe cooling plate 536, the electrostatic chuck 515 may be maintained atmuch greater temperatures than the cooling plate 536. For example, insome embodiments the electrostatic chuck 515 may be heated totemperatures of 200-300 degrees Celsius, while the cooling plate 536 maymaintain a temperature of below about 80 degrees Celsius. In oneembodiment, the electrostatic chuck 515 may be heated up to atemperature of about 250° C. while maintaining the cooling plate 536 ata temperature of about 60° C. or below. Accordingly, up to a 250° C.delta may be maintained between the electrostatic chuck 515 and thecooling plate 536 in embodiments. The electrostatic chuck 515 and thecooling plate 536 are free to expand or contract independently duringthermal cycling.

In one embodiment, a mounting plate 540 is disposed beneath and coupledto the base plate 595. In one embodiment, a thermal spacer 585 isdisposed on the base plate 595 (e.g., adjacent to the o-ring 545). Thethermal spacer 585 may be used to ensure that the base plate 595 willnot come into contact with the electrostatic chuck 515.

In one embodiment, one or more gas holes 532, 542 are drilled into thecooling plate 536, the base plate 595 and/or the electrostatic chuck515. The gas holes 532, 542 may be used to deliver a backside gas suchas helium to a backside of a chucked substrate. In one embodiment, theelectrostatic chuck 515 includes a gas hole 532 that terminates at aporous plug 534. The gas hole 532 may be a through hole that is counterbored with a larger diameter bore to permit the porous plug 534 to beinserted into the larger diameter bore. The porous plug 534 may be aporous ceramic such as AlN or Al₂O₃. The porous plug 534 may preventarcing and/or may prevent a plasma from being generated within theelectrostatic puck 505. The porous plug may have a porosity of anywherebetween about 30% to about 60%.

In one embodiment, the cooling plate 536 includes a hole, and the baseplate 595 includes a projection 544 that extends through the hole in thecooling plate 536. The hole 542 may be bored into the projection 544(e.g., into a center of the projection 544). In one embodiment, ano-ring 538 is disposed on a top of the projection 544. The fasteners 526may compress the o-ring 538 when tightened. The o-ring 538 may be a sametype of o-ring as o-ring 545 in embodiments.

FIG. 6A depicts a perspective view of one embodiment of a bottom of anelectrostatic chuck 600. The electrostatic chuck 600 is shown upsidedown to better show particular components of the electrostatic chuck600. As illustrated, the bottom of the electrostatic chuck 600 is flator approximately flat and defines a circle. Adapter objects 620, 624have been bonded to the bottom of the electrostatic chuck 600 using ametal bond. Each of the adapter objects 620, 624 includes one or morefeatures 622, 626. For example, adapter objects 620 near a periphery ofthe electrostatic chuck 600 include features 622 and adapter objects 624near a center of the circle defined by the bottom of the electrostaticchuck 600 include features 626. As illustrated, each adapter object 620,624 has a circular shape and includes a single feature 622, 626.However, in alternative embodiments adapter objects 620, 624 may havedifferent shapes, have different sizes and/or contain more than onefeature. For example, adapter objects 620, 624 may be square,rectangular, hexagonal, octagonal, or have other shapes.

Electrostatic chuck 600 may additionally include one or more lift pinholes 699 and/or a gas delivery hole 680. In the illustrated example, aline B1-B1′ is shown that passes through two outer adapter objects 620,two inner adapter objects 624 and the gas delivery hole 680. Theelectrostatic chuck 600 is similar to electrostatic chuck 400 exceptthat for electrostatic chuck 600 the adapter objects 620, 624 are bondedto the bottom surface of the electrostatic chuck rather than to holesbored in the bottom of the electrostatic chuck 400.

FIG. 6B depicts a perspective view of one embodiment of a bottom of anelectrostatic chuck 602. The electrostatic chuck 602 is shown upsidedown to better show particular components of the electrostatic chuck602. As illustrated, the bottom of the electrostatic chuck 602 is flator approximately flat and defines a circle. Two ring shaped adapterobjects 630, 640 have been bonded to the bottom of the electrostaticchuck 602 using a metal bond. Each of the adapter objects 630, 640includes multiple features 632, 642. For example, adapter object 630near a periphery of the electrostatic chuck 602 include features 632 andadapter object 640 near a center of the circle defined by the bottom ofthe electrostatic chuck 602 include features 642.

As illustrated, adapter object 630 and 640 each have a ring shape andincludes multiple features 632, 642. However, in alternative embodimentsadapter objects 630, 640 may have different shapes, have different sizesand/or contain different amounts of features. For example, anelectrostatic chuck may include one or more straight rectangular adapterobjects, some of which may include features near the center of theelectrostatic chuck as well as features near the periphery of theelectrostatic chuck. An electrostatic chuck may additionally oralternatively include adapter objects having a shape of a partial ringthat include multiple outer features or multiple inner features.

Electrostatic chuck 602 may additionally include one or more lift pinholes 699 and/or a gas delivery hole 680. In the illustrated example, aline B2-B2′ is shown that passes through adapter object 630, adapterobject 640 and the gas delivery hole 680. The electrostatic chuck 602 issimilar to electrostatic chuck 402 except that for electrostatic chuck602 the adapter objects 630, 640 are bonded to the bottom surface of theelectrostatic chuck rather than to trenches machined in the bottom ofthe electrostatic chuck 402.

FIG. 7 depicts a sectional side view of one embodiment of a substratesupport assembly 705. In one embodiment, substrate support assembly 705corresponds to substrate support assembly 150 of FIGS. 1-2. Thesubstrate support assembly 705 includes an electrostatic chuck 715, abase plate 795, a cooling plate 736 and a mounting plate 740.

In one embodiment, electrostatic chuck 715 corresponds to electrostaticchuck 600 of FIG. 6A. The sectional side view of FIG. 7 is shown at acut line that corresponds to line B1-B1′ of FIG. 6A in one embodiment.In one embodiment, electrostatic chuck 715 corresponds to electrostaticchuck 602 of FIG. 6B. The sectional side view of FIG. 7 is shown at acut line that corresponds to line B2-B2′ of FIG. 6B in one embodiment.

The electrostatic chuck 715 is composed of an electrically insulative(dielectric) ceramic such as AlN or Al₂O₃. The electrostatic chuck 715includes clamping electrodes 727 and one or more heating elements 729.The clamping electrodes 727 may be coupled to a chucking power source(not shown), to an RF plasma power supply (not shown) and/or to an RFbias power supply (not shown) via a matching circuit (not shown). Theheating elements 729 are electrically connected to a heater power source(not shown) for heating the electrostatic chuck 715.

An adapter object 752 is bonded to a bottom of electrostatic chuck 715by a metal bond 750. An adapter object 762 is also bonded to the bottomof the electrostatic chuck 715 by a metal bond 750. Adapter object 752includes one or more features 754. Adapter object 762 additionallyincludes one or more features 764. Each feature is configured to receivea fastener. Metal bonds 750 may be the same as metal bonds 550 that werepreviously described. The metal bond may be, for example, a metal bondformed by diffusion bonding or brazing. The adapter objects 752, 762 mayhave a thickness of about 5 mm to about 25 mm.

Preferably, the adapter objects 752, 762 are made of a material having aCTE that matches or is similar to a CTE of the electrostatic chuck 715.In one embodiment, the adapter objects 752, 762 are molybdenum. Inanother embodiment, the adapter objects are made of a nickel-cobaltferrous alloy such as Kovar®. In another embodiment, the adapter objects752, 762 are made of an electrically conductive metal matrix composite(MMC) material such as AlSiSiC.

The electrostatic chuck 715 may have a thickness of about 3-10 mm. Inone embodiment, the electrostatic chuck 715 has a thickness of about 3-5mm. The clamping electrodes 727 may be located about 0.3 to 1 mm from anupper surface of the electrostatic chuck 715, and the heating elements729 may be located about 2 mm under the clamping electrodes 727. Theheating elements 729 may be screen printed heating elements having athickness of about 10-200 microns. Alternatively, the heating elements729 may be resistive coils that use about 1-3 mm of thickness of theelectrostatic chuck 715. In such an embodiment, the electrostatic chuck715 may have a minimum thickness of about 5 mm.

In one embodiment, the electrostatic chuck 715 has a diameter of about300 mm. Alternatively, the electrostatic chuck 715 may have any otherdiameter. An edge of base plate 795 may have a similar diameter to thediameter of the electrostatic chuck 715. A plasma resistant and hightemperature o-ring 745 may be disposed between electrostatic chuck 715and the base plate 795. This o-ring 745 may provide a vacuum sealbetween an interior of the substrate support assembly 705 and aprocessing chamber. The o-ring 745 may be made of a perfluoropolymer(PFP). In one embodiment, the o-ring 745 is a PFP with inorganicadditives such as SiC. The o-ring 745 may be replaceable.

The base plate 795 includes a cooling plate 736 that may act as a heatsink for the electrostatic chuck 715. The material of the cooling plate736 may affect the heat transfer properties of the cooling plate 736.For example, an aluminum cooling plate 736 will transfer heat betterthan a stainless steel cooling plate 736.

The cooling plate 736 may be coupled to the base plate 795 by one ormore springs 770, which operate to press the heat sink 736 against theelectrostatic chuck 715. In one embodiment, the springs 770 are coilsprings. The springs 770 apply a force to press the heat sink 736against the electrostatic chuck 715. The electrostatic chuck 715 iscoupled to and in thermal communication with the cooling plate 736. Thecooling plate 736 has one or more conduits 735 (also referred to hereinas cooling channels) in fluid communication with a fluid source (notshown).

The cooling plate 736 and/or base plate 795 may be machined to have asurface profile that is an inverse of (e.g., a negative of) the surfaceprofile of the bottom of the electrostatic chuck 715 with the bondedadapter objects 752, 762. Accordingly, Where the adapter objects 752.762 protrude from the bottom of the electrostatic chuck 715 the coolingplate 736 and base plate 795 include recesses to accommodate theprotruding adapter objects 752, 762. In one embodiment, the recesseshave a depth of about 5 mm to about 25 mm, depending on the thickness ofthe adapter objects 752, 762.

The adapter objects 752, 762 may collectively include numerous features754, 764 for receiving fasteners. The base plate 795 may likewiseinclude multiple features 726 for accommodating the fasteners.Additionally, the cooling plate 736 may include multiple bores foraccommodating the fasteners. In one embodiment, the cooling plate 636and/or base plate 695 are coupled to the electrostatic chuck 715 bymultiple fasteners 728. The fasteners may be threaded fasteners such asbolts or nut and bolt pairs.

In one embodiment, the features 726 are bolt holes with counter bores.The features may be through features that extend through the base plate795. In one embodiment, the features 754, 764 are threaded holes in theadapter objects 752, 762. Alternatively, the features may be holesand/or slots that accommodate a t-shaped bolt head or rectangular nutthat may be inserted into the slot and then rotated 90 degrees. In oneembodiment, the fasteners include washers, grafoil, aluminum foil, orother load spreading materials to distribute forces from a head of thefastener evenly over a feature. In one embodiment, a helical insert(e.g., a Heli-Coil®) or other threaded insert (e.g., a press fit insert,a mold-in insert, a captive nut, etc.) may be inserted into features 754to add a threaded hole thereto. A bolt placed inside of the coolingplate 736 and/or base plate 795 (e.g., inside features 726 in the baseplate 795, through the cooling plate 736) and protruding from thecooling plate 736 may be threaded into the threaded insert or threadedfeature to secure the cooling plate to the electrostatic chuck.Alternatively, threaded inserts may be used in the cooling plate.

In one embodiment, a captive nut, mold insert, press fit insert, orother threaded insert is positioned inside of features 754, 764 in theadapter objects 752, 762. In one embodiment, the features 754, 764 arethreaded holes that are brazed prior to insertion of a threaded rod intothe features 754, 764. A metal bonding (e.g., diffusion bonding)procedure may then be performed to secure the threaded rod to thefeature 754, 764. This may provide increased durability for applicationof increased force during assembly.

The cooling plate 736 may act as a heat sink to absorb heat from theelectrostatic chuck 715. In one embodiment (as shown), a low thermalconductivity gasket 725 is disposed on the cooling plate 736. The lowthermal conductivity gasket 725 may be, for example, a PFP gasket or astack of alternating layers of polyimide and grafoil.

The fasteners 728 may be tightened with approximately the same force toevenly compress the low thermal conductivity gasket 725. The low thermalconductivity gasket 725 may decrease heat transfer between theelectrostatic chuck 715 and the cooling plate 736 and act as a thermalchoke. In one embodiment, a grafoil layer (not shown) is disposed overthe low thermal conductivity gasket 725. The grafoil may have athickness of about 10-40 mil, The fasteners may be tightened to compressthe grafoil layer as well as the low thermal conductivity gasket 725.The grafoil may be thermally conductive.

By maintaining a thermal choke between the electrostatic chuck 715 andthe cooling plate 736, the electrostatic chuck 715 may be maintained atmuch greater temperatures than the cooling plate 736. For example, insome embodiments the electrostatic chuck 715 may be heated totemperatures of 200-300 degrees Celsius, while the cooling plate 736 maymaintain a temperature of below about 120 degrees Celsius. In oneembodiment, the electrostatic chuck 715 may be heated up to atemperature of about 250° C. while maintaining the cooling plate 736 ata temperature of about 60° C. or below. Accordingly, up to a 190° C.delta may be maintained between the electrostatic chuck 715 and thecooling plate 736 in embodiments. The electrostatic chuck 715 and thecooling plate 736 are free to expand or contract independently duringthermal cycling.

In one embodiment, a mounting plate 740 is disposed beneath and coupledto the base plate 795. In one embodiment, a thermal spacer 785 isdisposed on the base plate 795 (e.g., adjacent to the o-ring 745). Thethermal spacer 785 may be used to ensure that the base plate 795 willnot come into contact with the electrostatic chuck 715.

In one embodiment, one or more gas holes 732, 742 are drilled into thecooling plate 736, the base plate 795 and/or the electrostatic chuck715. The gas holes 732, 742 may be used to deliver a backside gas suchas helium to a backside of a chucked substrate. In one embodiment, theelectrostatic chuck 715 includes a gas hole 732 that terminates at aporous plug 734. The gas hole 732 may be a through hole that is counterbored with a larger diameter bore to permit the porous plug 734 to beinserted into the larger diameter bore. The porous plug 734 may be aporous ceramic such as AlN or Al₂O₃. The porous plug 734 may preventarcing and/or may prevent a plasma from being generated within theelectrostatic puck 705. The porous plug may have a porosity of anywherebetween about 30% to about 60%.

In one embodiment, the cooling plate 736 includes a hole, and the baseplate 795 includes a projection 744 that extends through the hole in thecooling plate 736. The hole 742 may be bored into the projection 744(e.g., into a center of the projection 744). In one embodiment, ano-ring 738 is disposed on a top of the projection 744. The fasteners 728may compress the o-ring 738 when tightened. The o-ring 738 may be a sametype of o-ring as o-ring 745 in embodiments.

FIG. 8 illustrates one embodiment of a process 800 for manufacturing asubstrate support assembly. At block 805 of process 800, recesses areformed in either a bottom of an electrostatic chuck or in a top of acooling plate and/or a top of a base plate. At block 810, two or moreadapter objects are bonded to the bottom of the electrostatic chuck. Ifrecesses were formed in the bottom of the electrostatic chuck, then theadapter objects are bonded into the recesses. If recesses were formed inthe cooling plate and/or base plate, then the adapter objects are bondedto the bottom of the electrostatic chuck at locations that will alignwith the recesses. The adapter objects may be formed of AlSiSiC plate,Molybdenum, or another suitable material. Each of the adapter objectsincludes one or more features for accommodating fasteners.

At block 815, a gasket is disposed on a top side of a cooling plate. Thecooling plate may be, for example, an aluminum or aluminum alloy coolingplate with multiple channels to flow a cooling fluid. The gasket may bePFP or an alternating stack of polyimide and grafoil. The cooling plateand/or base plate may also have features formed therein. The features inthe cooling plate and/or base plate and the features in the lower puckplate may each accommodate a fastener (e.g., a bolt and/or nut).

At block 820, fasteners are inserted into the features in the adapterobjects and/or the base plate. At block 825, the electrostatic chuck iscoupled to the base plate by tightening the fasteners (e.g., bythreading bolts protruding from the features in the lower puck plateinto nuts residing in the features in the cooling plate.

The preceding description sets forth numerous specific details such asexamples of specific systems, components, methods, and so forth, inorder to provide a good understanding of several embodiments of thepresent invention. It will be apparent to one skilled in the art,however, that at least some embodiments of the present invention may bepracticed without these specific details. In other instances, well-knowncomponents or methods are not described in detail or are presented insimple block diagram format in order to avoid unnecessarily obscuringthe present invention. Thus, the specific details set forth are merelyexemplary. Particular implementations may vary from these exemplarydetails and still be contemplated to be within the scope of the presentinvention.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment. Thus, the appearances of the phrase “in oneembodiment” or “in an embodiment” in various places throughout thisspecification are not necessarily all referring to the same embodiment.In addition, the term “or” is intended to mean an inclusive “or” ratherthan an exclusive “or.” When the term “about” or “approximately” is usedherein, this is intended to mean that the nominal value presented isprecise within ±10%.

Although the operations of the methods herein are shown and described ina particular order, the order of the operations of each method may bealtered so that certain operations may be performed in an inverse orderor so that certain operation may be performed, at least in part,concurrently with other operations. In another embodiment, instructionsor sub-operations of distinct operations may be in an intermittentand/or alternating manner. In one embodiment, multiple metal bondingoperations are performed as a single step.

It is to be understood that the above description is intended to beillustrative, and not restrictive. Many other embodiments will beapparent to those of skill in the art upon reading and understanding theabove description. The scope of the invention should, therefore, bedetermined with reference to the appended claims, along with the fullscope of equivalents to which such claims are entitled.

What is claimed is:
 1. An electrostatic chuck comprising: a ceramicbody; and a plurality of adapter objects that collectively form aplurality of openings distributed over a bottom surface of the ceramicbody at a plurality of different distances from a center of a circledefined by the bottom surface of the ceramic body.
 2. The electrostaticchuck of claim 1 further comprising at least one of: one or more heatingelements disposed in the ceramic body; or one or more electrodesdisposed in the ceramic body.
 3. The electrostatic chuck of claim 1,wherein the plurality of adapter objects are bonded to the bottomsurface of the ceramic body by a metal bond.
 4. The electrostatic chuckof claim 1, wherein a first opening of the plurality of openings is tocouple to a fastener to secure a base plate against the bottom surfaceof the ceramic body.
 5. The electrostatic chuck of claim 1, wherein theplurality of distances comprise a first distance from the center and asecond distance from the center, and wherein the plurality of adapterobjects comprise: an inner ring or inner disc having a first diameter,the inner ring or inner disc comprising a first subset of the pluralityof openings that have the first distance from the center; and an outerring having a second diameter, the outer ring comprising a second subsetof the plurality of openings that have the second distance from thecenter.
 6. The electrostatic chuck of claim 1, wherein the plurality ofadapter objects comprise: a plurality of discs, each of the plurality ofdiscs comprising one of the plurality of openings.
 7. The electrostaticchuck of claim 1, wherein the bottom surface of the ceramic body formsat least one recess, wherein at least one adapter object of theplurality of adapter objects is inserted into the at least one recess,and wherein a bottom of the at least one adapter object is approximatelyflush with the bottom surface of the ceramic body.
 8. The electrostaticchuck of claim 1, wherein the plurality of adapter objects comprise atleast one of a) Molybdenum, b) a nickel-cobalt ferrous alloy, c) a SiCporous body infiltrated with an AlSi alloy, or d) a metal matrixcomposite comprising Si, SiC, and Ti.
 9. The electrostatic chuck ofclaim 1, wherein the ceramic body comprises AlN or Al₂O₃, and whereineach of the plurality of adapter objects comprises at least one of ametal, a metal alloy, or a metal matrix composite.
 10. A substratesupport assembly comprising: an electrostatic chuck comprising one ormore objects, wherein collectively the one or more objects comprise aplurality of features distributed over a bottom of the electrostaticchuck at a plurality of different distances from a center of a circledefined by the bottom of the electrostatic chuck.
 11. The substratesupport assembly of claim 10, wherein collectively the plurality offeatures accommodate a plurality of fasteners.
 12. The substrate supportassembly of claim 11, wherein the plurality of fasteners comprise aplurality of threaded fasteners and the plurality of features comprise aplurality of openings for receiving the plurality of threaded fasteners.13. The substrate support assembly of claim 11 further comprising: abase plate coupled to the electrostatic chuck by the plurality offasteners, wherein the plurality of fasteners each apply anapproximately equal fastening force to couple the base plate to theelectrostatic chuck.
 14. The substrate support assembly of claim 13further comprising: a first gas delivery passage in the base plate; asecond gas delivery passage in the electrostatic chuck that lines upwith the first gas delivery passage in the base plate; and a secondo-ring at a border of the first gas delivery passage and the second gasdelivery passage to provide a seal.
 15. The substrate support assemblyof claim 13 further comprising: an o-ring disposed between theelectrostatic chuck and the base plate at a periphery of theelectrostatic chuck, wherein the o-ring is to provide a vacuum sealbetween the electrostatic chuck and the base plate.
 16. The substratesupport assembly of claim 13 further comprising: a cooling platedisposed in a recess of the base plate, the cooling plate comprising aplurality of channels to receive a coolant.
 17. The substrate supportassembly of claim 16, wherein the one or more objects form a patternthat projects from the bottom of the electrostatic chuck, wherein a topof the cooling plate forms a plurality of recesses that form a negativeof the pattern, and wherein the pattern that projects from the bottom ofthe electrostatic chuck fits into the negative of the pattern in the topof the cooling plate.
 18. The substrate support assembly of claim 16,wherein one or more springs connect a bottom surface of the coolingplate to the base plate.
 19. The substrate support assembly of claim 18,further comprising: a gasket disposed on a top side of at least aportion of the cooling plate, wherein the gasket is compressed betweenthe cooling plate and the electrostatic chuck and acts as a thermalchoke between the cooling plate and the electrostatic chuck, wherein theone or more springs cause the cooling plate to press against theelectrostatic chuck.
 20. The substrate support assembly of claim 19,wherein the gasket comprises: a first grafoil layer; a first polyimidelayer on the first grafoil layer; a second grafoil layer on the firstpolyimide layer; a second polyimide layer on the second grafoil layer;and a third grafoil layer on the second polyimide layer.